A scissor lift is a type of lift that can usually only move vertically. The mechanism to achieve this is the use of linked, folding supports in a single or criss-cross “X” pattern, known as a scissor mechanism or pantograph. The upward motion is achieved by the application of pressure to the lowest set of supports, elongating the crossing pattern, and propelling a platform vertically.
The extension and contraction of the scissor action can e.g. be hydraulic, pneumatic or mechanical (via a leadscrew or rack and pinion system). In hydraulic and pneumatic systems, it may require no power to enter “descent” mode, but rather a simple release of hydraulic or pneumatic pressure. This is the main reason that these methods of powering the lifts are preferred, as it allows a fail-safe option of returning the platform to a contracted state by release of a manual valve.
However, the power required to move the platform upwards is very uneven over the full stroke of the platform in a traditional scissor lift design. The power required to extend the lift at the beginning of the stroke is up to or even more than ten times greater than the power required to move the lift upwards at the end of the stroke, under the same load.
Thus, from the international patent application WO 99/62813 it is therefore known to provide a scissor lift with a gearing mechanism which ensures that the power required to move the platform upwards is more evenly distributed over the full stroke of the platform. However, the lift according to WO 99/62813 still requires up to 30% more power to move the platform at the beginning of the stroke than at the end of the stroke.
The invention therefore provides for scissor lift with a more advantageous power requirement distribution during the entire stroke.